351 running on 6 under 2000 revs - Ford Forums - Mustang Forum, Ford Trucks, Ford Focus and Ford Cars
Ford Forum Ford Forum

» Auto Insurance
» Featured Product
ยป Wheel & Tire Center

Go Back   Ford Forums - Mustang Forum, Ford Trucks, Ford Focus and Ford Cars > The Garage - Tech Forums > General Tech
Register Home Forum Active Topics Photo Gallery Auto Loans Garage Mark Forums Read Auto Escrow

General Tech Have a question that is not covered by one of the other categories? This is the forum for all other items not specifically covered in other categories.

FordForums.com is the premier Ford Forum on the internet. Registered Users do not see the above ads.
Reply
 
LinkBack Thread Tools Display Modes
Old 09-22-2005, 01:06   #1 (permalink)
Registered User
 
Join Date: Mar 2005
Posts: 55
351 running on 6 under 2000 revs

351 clevo running on six under 2000 revs until u apply gas then it picks back up 2 8, does not break down at high revs changed coil ,plugs leads have been thru the basics and not having much joy ive heard the duraspark dizzy setup is known 4 probs like this any ideas?
472gt is offline   Reply With Quote
Sponsored Links
Advertisement
 
Old 09-22-2005, 01:10   #2 (permalink)
Registered User
 
TruBlu351's Avatar
 
Join Date: Apr 2003
Location: Newcastle
Posts: 2,398
Re: 351 running on 6 under 2000 revs

Can you isolate it to the 2 bad cylinders?

ie: take the leads off at idle and see which ones don't make it worse.

Is it ROUGH causing you to say 6 cylinders or 2 are dropping out? ie: could it be carby etc?

Other things.........Dissy cap/rotor?
__________________
XE Falcon
393 Tremec TKO 9"
TruBlu351 is offline   Reply With Quote
Old 09-22-2005, 03:13   #3 (permalink)
Registered User
 
Join Date: Mar 2005
Posts: 475
Re: 351 running on 6 under 2000 revs

I've had this exact problem on cars fitted with a Carter Thermoquad. The little quad rings start to leak, and the engine basically floods at low revs. Normally only one will leak, so that gives you 4 cylinders straight away (dual plane manifold), and due to the different runner lengths between the middle two cyliders and the end two cylinders, the miss only shows up on two......
RPO-083 is offline   Reply With Quote
Old 09-22-2005, 12:22   #4 (permalink)
Registered User
 
Join Date: Mar 2005
Posts: 55
Re: 351 running on 6 under 2000 revs

Quote:
Originally Posted by RPO-083
I've had this exact problem on cars fitted with a Carter Thermoquad. The little quad rings start to leak, and the engine basically floods at low revs. Normally only one will leak, so that gives you 4 cylinders straight away (dual plane manifold), and due to the different runner lengths between the middle two cyliders and the end two cylinders, the miss only shows up on two......
this sounds about right like its flooding until u stamp on the gas what do u mean by quad rings do the 780 holleys? would blown power valve cause this?
472gt is offline   Reply With Quote
Old 09-22-2005, 12:29   #5 (permalink)
Registered User
 
Join Date: Mar 2005
Posts: 55
Re: 351 running on 6 under 2000 revs

Quote:
Originally Posted by RPO-083
I've had this exact problem on cars fitted with a Carter Thermoquad. The little quad rings start to leak, and the engine basically floods at low revs. Normally only one will leak, so that gives you 4 cylinders straight away (dual plane manifold), and due to the different runner lengths between the middle two cyliders and the end two cylinders, the miss only shows up on two......
do the 780 holleys have a setup like this ?as this sounds very similar 2 what it is doing flooding until u stamp on the gas. could a blown power valve in carby cause these symptons ?
472gt is offline   Reply With Quote
Old 09-22-2005, 12:33   #6 (permalink)
Registered User
 
Join Date: Mar 2005
Posts: 55
Re: 351 running on 6 under 2000 revs

Quote:
Originally Posted by TruBlu351
Can you isolate it to the 2 bad cylinders?

ie: take the leads off at idle and see which ones don't make it worse.

Is it ROUGH causing you to say 6 cylinders or 2 are dropping out? ie: could it be carby etc?

Other things.........Dissy cap/rotor?
it is probably running rough more so than dropping 2 cylinders unable 2 isolate the cylinders. have new cap and rotor on also
472gt is offline   Reply With Quote
Old 09-22-2005, 23:44   #7 (permalink)
Registered User
 
TruBlu351's Avatar
 
Join Date: Apr 2003
Location: Newcastle
Posts: 2,398
Re: 351 running on 6 under 2000 revs

Blown power valves generally make your car idle really RICH, and the exhaust makes your eyes water like cutting onions!

You can try running the mixture screws right in (LEAN) and look for any improvement. If your car still runs (with mixture screws all the way in), then it could be a leaky power valve, or the throttle plates are a too far open (idle screw) and the transition circuit is providing fuel.
__________________
XE Falcon
393 Tremec TKO 9"
TruBlu351 is offline   Reply With Quote
Old 09-23-2005, 01:34   #8 (permalink)
Registered User
 
Join Date: Mar 2005
Posts: 475
Re: 351 running on 6 under 2000 revs

Quote:
Originally Posted by 472gt
this sounds about right like its flooding until u stamp on the gas what do u mean by quad rings do the 780 holleys? would blown power valve cause this?
Nah, different setup between Thermoquad and Holley. The Carters have little square o-rings (quad rings) between the top and middle housings to seal the fuel passage to the main jets. When one leaks, you get overfueling to two (sometimes four depending on how bad a leak) cylinders only, which gives a miss.

The Holley basics have been posted above; progressive ports, power valve, etc.
RPO-083 is offline   Reply With Quote
Old 09-23-2005, 06:37   #9 (permalink)
Registered User
 
Freshmeat's Avatar
 
Join Date: Sep 2005
Location: Geismar, LA, USA
Age: 31
Posts: 833
Re: 351 running on 6 under 2000 revs

Rebuild the carb and be done with it. It costs about $25(US) and it only took me 45 minutes to rebuild the Holley 598 that was on my Mustang. It's easy and you can get very specific instructions on how to do it. End of problem.
__________________

My Garage
Freshmeat is offline   Reply With Quote
Sponsored Links
Advertisement
 
Reply

  Ford Forums - Mustang Forum, Ford Trucks, Ford Focus and Ford Cars > The Garage - Tech Forums > General Tech



Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Powered by vBadvanced CMPS v3.2.2

All times are GMT -7. The time now is 14:16.



Powered by vBulletin® Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Content Relevant URLs by vBSEO 3.6.0
Garage Plus vBulletin Plugins by Drive Thru Online, Inc.